Cutter teeth for well drills



Nov. 9, 1943.-

F. L. sco'r-r :1- AL CUTTER TEETH FOR WELL DRILLS Filed July 11, 1940 2 Sheets-Sheet l ATTORNEY Nov. 9, 1943.

F. L. sco'r'r ET AL I CUTTER TEETH FOR WELL DRILLS 2 sh et's-snee 2 Filed July 11, 1940 1 19 0 L Scott lz'erbert L 6'0 IN V EN TOR.

BY M 6AM I A TTORNEYS.

having teeth formed on Patented Nov. 9, 1943 UNITED STATES 2,333,746 CUTTER TEETH FOB- WELL DRJLLS Floyd L. Scott, Lewis E.

Cockrum, Houston, Tex., Tool Company, Housto Delaware Garfield, and Herbert L; assignors to. Hughes n, Tex., a corporation of Application July 11, 1940, Serial No. 344,876

4 Claims.

Our'inventio'n relates to roller earthrboring well drills and particularly to the formation of the teeth upon the drill cutters.

Rotary earth boring drills of the roller type are rovided with one or more rolling cutters the working surface to engage and cut the bottom of the well bore.

These teeth tend to generate tracks or imprints in the formation, hereinafter the bottom of the well bore. The tracks or imprints cut in the rock will hereinafter be called rock teeth to distinguish them from the teeth of the cutters. As each cutter rolls upon the well bottom, the teeth thereon engage the flanks and roots of these so-called rock teeth previously cut by them or the teeth of other cutters, so that the rock teeth are chipped and broken off and the .well bottom is thus disintegrated.

The speed of drilling depends to a great extent upon the depth of penetration in the formation being drilled by the cutter teeth at each round of the well bottom. This penetration depends, in any given formation, upon the tooth contact on bottom, that is, the sum of the length of the crests of all the teeth, which are in contact with the bottom at any one time. Thus, if a weight of ten tons is allowed to rest upon the drill, the tooth crests thus in contact with the bottom will support that load between them. If the contacting tooth crest areas taken together are relatively small, then the ten tons of weight will cause the teeth to penetrate deeper than if the tooth crest areas were larger.

A roller well drill commonly used is the conebit having two or three approximately conical shaped cutters mounted on the drill head to roll upon the well bottom. The base or heel teeth of these cutters cut the formation adjacent the Fig. 3 is a broken detail showing a section wall of the hole. Particularly where three outthrough an interrupted heel tooth on a drill cutters are used there are more teeth in contact 40 ter. 7

with the bottom of the hole than is the case with Fig. 4 is a side elevation of a side cutter upon other well known types of drills. Where light weights are employed, as where a straight hole is desired, this extra tooth contact causes poor penetration and slows down the drilling rate. If the heel teeth are made narrower as by circumferential grooves they become weaker and thus easily broken. Also excessive narrowing of the teeth by such grooving tends to leave ridges of uncut bottom which slows down the progress of the drill.

It is, therefore, an obiect reduce the area of tooth contact upon bottom without teeth.

of the invention to the well 5 performance of the cutters.

termed rock, on

impairing the strength of the V in accordance with this invention. A plurality 7 It isaiso an object of this invention to so form the teeth upon rolling cutters used on well drills that there will'be a minimum of tooth contact upon well bottom consistent with good cutting It is desired that the rock teeth formed upon the well bottom have the same spacing as when teeth of combined larger areas are used. Better penetration is obtained with resultant greater .drilling speed, than can be obtained from cutter teeth formed in the customary manner.

It is an object to form well drill cutters in the same general construction as is now customarily used, but to eliminate a part of the area of cutting teeth in contact with the bottom at any one time.

It is an object to provide a cutter having full crested teeth interspaced with shorter crested teeth, said teeth being arranged such that each rock impression made by shorter crested teeth is engaged by full crested teeth on succeedin .rounds.

We also aim to provide greater amount of space on the cutter into which the material dislaced by the cutter teeth may move and thus be better carried away by the flushing fiuid and by so doing avoid clogging of the cutter by they formation being drilled.

For a better explanation of the character of the invention, reference is made to the drawings herewith wherein:

Fig. 1 is a side elevation of a cutter of a. three cone bit a portion of the drill head being shown in section.

Fig. 2 is a plan view showing how rock teeth are formed on the well bottom by the teeth of the cutters upon a three cone bit.

:1 cross roller type of drill embodying the inven- Fig. 5 is a similar view of a core drill cutter showing a slightly different embodiment of the invention.

Fig. 6 is a bottom plan view of three companion cutters illustrating the invention.

Fig. I is a. broken detail showing a still different embodiment of the invention.

must-rating ourinvention as applied to a well drill with two or more conical shaped cutters, Fi 1 shows a cone bit cutter of well known con struction, but having the teeth thereon formed of cutters, preferably two or three, are mounted upon a bit head I, in a position inclined thereto. as shown. The cutter encloses the end of a. Shaft upon which it is rotatably mounted. Said cutter is approximately conical in shape and is commonly called a cone by well drillers. There are circumferential rows of teeth around the surface of the cutter, said rows being spaced apart. Y

The row 2 of teeth adjacent the base of the cutter is commonly called the heel row and the teeth therein are referred to as heel teeth. This row of teeth is subjected to the hardest usage. As these heel teeth traverse a track of largest circumference, they cut a large part of the hole.

Also as they cut adjacent the wall 3 of the hole, they have to maintain the gage of the hole and cut in the angular portion 4 where the bottom and side of the hole meet and where the material is not so easily displaced in drilling as is the material upon the open bottom of the hole. These teeth are formed with longer crests 5, than are the crests 6 of teeth 1 in the next inner adjacent row. The length of the crests upon the heel teeth on different cutters may be understood as different upon each cutter from the length upon any of the others and also although teeth of the same pitch on all the cutters is desirable, the number of teeth in each row of heel teeth may be difierent upon different cutters. This is old and well accepted practice and is not, therefore, illustrated.

To obtain as small an amount of tooth crest area in contact with the bottom of the hole as possible we have formed some of the heel teeth upon the cutter with crests that are shorter than those on other teeth in that row. These teeth we call interrupted teeth. In Fig. 1 the gage end of every other tooth has been removed, as shown at 8, for about half the length of the tooth. By reference to Fig. 3 it will be seen that this does notremove all of the gage cutting surface 9 of the cut-away tooth and hence the interrupted tooth will still be able to do a part in maintaining the gage of the hole. The crests a of the interrupted teeth, although of shorter length than the other teeth will have to support their share of the load sustained by the whole drill and will therefore cause deeper penetration for all teeth.

By forming some of the teeth with shorter supporting crests greater space at 8 is provided into which material displaced by the chisel stroke of the tooth may be moved. Flushing fluid in the hole can better engage and carry away the displaced material, thus preventing balling-up of the cutter teeth. A

It is to be" noted that this way of reducing the amount of tooth crest on bottom still results instrong sturdyteeth as compared with the old way of making. two or more circumferential rows at the heel as indicated by the dotted lines in Fig. 3. For if this heel tooth were reduced in crest area by cutting away the notch 8a, the two teeth thus formed of each heel tooth would be narrow and easily broken off. This can best be understood from Fig. 6.

To prevent the formation of rock teeth on bottom which might stand-up high enough to engage in spaces such as l9 between adjacent teeth and thereby hold up the progress of the drill, we.

take steps to assure that the teeth in the rows do not continually track in the previous imprints made by them upon the well bottom. Thus the teeth in each row cannot be regularly and uniformly interrupted. Where they are interrupted in groups of two-one tooth deleted and the next one, not-then the number of groups must not be integral. Also, if the number of heel teeth are .divisible by three, the interruption of the teeth In rolling upon the well bottom the teeth will function in the usual manner. The interrupted teeth will not continually fall into the same impressions made by them on preceding rolmds. Full crested teeth wfll cut out to the wall of the hole and will result in cutting rock teeth Ill upon bottom as shown in Fig. 2. We have found that there is no appreciable difference between the rock teeth on bottom cut by cutters with interrupted teeth and rock teeth out by cutters where there are none interrupted, that is, where the crests run the full length of all the teeth. The rock teeth upon the well bottom will hence be broken 01f and disintegrated 'just as well, as in the use of the ordinary cutter and the penetration of the teeth and the removal of the material disintegrated will be improved. Thus greater speed of drilling is obtained without shortening the life of the cutters.

When this invention is applied to rows of teeth on the cutter other than the heel row, as to the row of teeth I, for example, some of the teeth are completely removed leaving a blank space l1 in place thereof. Every alternate tooth, or every third tooth, may be omitted or the spaces may be irregularly arranged, as desired.

Our invention is applicable generally to all types of rolling cutters.

When considering the three cutters on a three cone drill, cooperating to cut the well bottom, it is apparent that further interruption of the teeth on the cutters may be made. We find that only one of the cutters need have all its teeth, particularly in the heel row, and some of these teeth may be partly removed. In Fig. 6 the cutters are identified as A, B and C. Both cutters A and B have had every other heel tooth entirely removed. As there are an uneven number of teeth in the rows, however, there is one place on each row where two teeth will remain uninterrupted side by side, as at l8. Where the teeth are omitted, the space I! left vacant is the full width of a tooth so that the'teeth remaining will be properlyspaced to engage in the grooves between rock teeth on bottom. 0n the cutter C the altenate teeth willbe interrupted for approximately half their crest lengths, as was done in the Fig. 1 embodiment. The other rows of teeth on each cutter inside the heel row may be interrupted or not as desired, and in Fig. 6 they are shown as uninterrupted.

When this drill is rotated, the cutters will roll upon the well'bottom and the cutter C will lay down the imprints into which the teeth on cutters A and B will fall. As an example, cutter C may have fifteen teeth, counting all the teeth in the heel row, and will have to 'rotate in excess of one revolution of the cutter before it completes the round of the well bottom. In observed cases a cutter with fifteen teeth in the heel row will form eighteen rock teeth on bottom in one rotation of the drill. Thu, as each cutter roteeth will be improved. The cutters A and B with only about half the usual number of heel ting crests of the teeth so that greater penetration can be obtained and greater untoothed area .be provided for the inclusion of the cuttings.

teeth will present a materially smaller tooth con tact on bottom. The remaining teeth in each row will, because of their spacing, fall into difierent imprints on each round of the bottom than they do on the immediately preceding or following rounds and will hence do their parts in cutting away and distintegrating the wellbottom. VTith difierent sizes of cutters or different pitches of teeth, the example given above may, of course, be varied.

The action upon the gage surface, in cutters such as A and B will be improved somewhat if 4 short teeth such as zll in Fig. '7 be formed in the spaces l9. The crests 2| on these teeth perform little or no service in cutting the well bottom, but they. engage the side wall of the hole and act materially to cut the wall and maintain the gage of the hole.

It will be obvious from 7 tion of teeth 22 will not be interfered with by the short teeth 20. We contemplate, therefore, that such intermediate teeth may be employed ghlere found desirable in maintaining a full sized In Fig. 4 the invention is shown as inco rated into a well drill having disc shaped cutters H, such, for example, as are used upon cross roller drills. Such cutters have longitudinal teeth l2 extending the full length of the cutter and alternate teeth l3 which have the gage .ends cut away adjacent the base of the cutter at It similarly to the interrupted teeth upon a cone drill previously described. It will "be obvious,therelore that the effect in the operation of the drill will be the same as in the first embodiment.

. There will be an increased penetration of the cutting teeth and a larger space to accommodate the displacing of the material upon the well bottom.

t their crests. Alternate teeth are cut away adjacent the gage or base ends. and the others are cutaway adjacent the inner or smaller end of the In Fig. 5 the teeth are all interrupted a cutter,- as shown at l6. In each case we obtain a similar effect. The practice of. cutting away ofpart of the crest of each tooth can be best adapted for use on drills where a larger number of cutters are employed to do the cutting; as in case of core drills, and cone drills for example. In such cases the same increase in speed of drilling is obtained for the reasons previously explained.

It is not necessary in this invention that the crests of the teeth be interrupted with regularity or that each alternate tooth be affected. The invention consists in reducing the area or the cutthat the perletratings by the flushing fluid. It is to be understood that any or all of the arrangements for the forming of the tooth crests illustrated in the drawings may be employed upon any of the diiferent forms of the cutters illustrated.

What weclaimasnewis: V

1. In a well drill, a. tapered cutter rotatably mounted thereon, said cutter having a row of heel teeth circumierentially thereof to cut the outer portion of the well bottom, some of the teeth in said row having a portion projecting from the cutter surface a shorter height than the others, thus providing on said shorter teeth an open area normally out of contact with the well bottom so as to allow cleaning of the cutter by the flushing fluid, and a gage cutting surface on the outer ends of all said teeth to en age the wall of the well.

2. A drill head, three approximately conical cutters mounted rotatably thereon, said cutters having circumferentially arranged rows of teeth thereon which together cut the full bottom of the hole, successive teeth in the outer row upon two of said cutters being spaced apart to provide having the outer row of .teeth closely spacedv thereon in said outer row.

3. In a well drill, a plurality of cutters tapered toward one end and each mounted onan inclined axis to roll upon the well bottom, said cutters having rows of cutting teeth around the circumference of the same, said teeth having cutting crests thereon positioned to cut a track on the well bottom, the row at the larger end of one of said cutters having the crest of each alternate tooth extending about one-half the length of the crests of the teeth adjacent thereto in the row, said short crested teethhaving formation receiving areas thereon,- the others of said cutters having widely and uniformly spaced teeth in the outer row, except at one point where two teeth are closely spaced to throw the uniformly spaced. teeth out of step on the well bottom on succeed- .ing rotations of the cutters thereon.

4. In a well drill, an inwardly tapering cutter having a row of teeth circu'mferentially around the same, the outer ends of which are positioned to cut the side wall of the hole, there being 

